1. Field of the Invention
This invention generally relates to power-driven angiographic syringes, and specifically to a plunger for such a syringe, and the syringe comprising same.
2. Description of the Related Art
In the field of angiography, a contrast medium of suitable indicating character (radiopacity) is introduced under pressure into coronary arteries, and the arterial network then is monitored by fluoroscopic or other visualizing means. As a result, arterial plaque deposits and/or other arterial occlusions are readily visually determined as to their size and location, so that suitable treatment methods, such as removal of the occuluding material by lasing or mechanical excision, or displacement techniques such as ballon angioplasty, may be carried out.
To effect the introduction of the contrast medium into the arterial network for angiographic study, it has been common practice to utilize injector syringes in combination with arterial catheters. The syringe may be machine-mounted in a so-called "power injector" apparatus, with the distal end of the syringe being connected to the catheter which is introduced into the arterial system to be studied.
There is disclosed in U.S. Pat. No. 4,677,980 issued Jul. 7, 1987 to D. M. Reilly, et al, an angiographic power injector featuring a rotating turret for housing multiple angiography syringes in readiness for injection. In use, the turret is selectively rotated to align an angiographic syringe with a driving mechanism of the power injector. Specifically, as is shown in FIGS. 9 and 10 of this patent, the plunger of the angiographic syringe may be configured with rearwardly extending hook members which are engaged by the head and stem portion (typically termed a "ram" in the field) of the driving mechanism.
In the plunger configuration disclosed in this patent, the hook elements on the proximal face of the plunger are diametrally opposed to one another, to form a slot therebetween through which the ram head is inserted and subsequently rotated, the head being of transversely extending character, so that it thereby engages the respective hook members. In this manner, the head and stem of the driving mechanism and the hook members are described to constitute a quick release driving connection, with the driving mechanism head fitting into the aperture formed by the hook members, and with the stem extending out from the aperture through the access slot between the hook members.
The Reilly et al patent, at column 6, lines 24-52 thereof, describes the subsequent operation of the coupled syringe, as comprising the forward translation of the driving mechanism to drive the plunger through the syringe to expel air therefrom, followed by connection of the syringe to a source of contrast media and retraction of the driving mechanism to pull the plunger back through the syringe, to draw contrast media thereinto, and finally advancement of the driving mechanism to drive the plunger distally in the syringe and effect injection of the contrast media through the catheter attached to the syringe. The patent states that after the injection has been carried out, the driving mechanism may be disengaged from the plunger, without reversing its movement, by the simple expedient of rotating the driving mechanism 90.degree., so that the driving mechanism head extends from the aperture on either side (see FIG. 10 of the patent). Subsequent retraction of the driving mechanism results in the head and stem of the driving mechanism being withdrawn from the aperture and slot thereby disengaging the driving mechanism from the plunger.
As a result of the foregoing configuration of the driving mechanism, and the hook members on the plunger, the risks incident to retracting the plunger through the syringe during the angioplasty procedure are said to be eliminated, and the mating hook members and driving mechanism head are said to cooperate so that the plunger can be placed in either a driven retractable state, or an undriven non-retractable state, at any time during the injection operation and at any position of the plunger, without substantial force being applied therebetween.
While the foregoing configuration of the hook members on the plunger facilitates the engagement and disengagement of the driving mechanism, without change in the position of the plunger, it also is true that the hook members themselves provide only a very small contact area for mating with the head of the driving mechanism, when the driving mechanism is in driving or retraction engagement with the hook members.
There is thus the danger that the head of the driving mechanism may disengage from contact with the hook members during operation of the syringe, so that subsequent rotation of the driving mechanism to effect disengagement actually effects re-engagement of the driving mechanism with the hook members, in turn causing retraction of the plunger, an occurrence which specifically is desired to be avoided.
The Reilly et al patent discloses other plunger and driving mechanism constructions, e.g., as shown in FIGS. 11-21 of the patent, but all such alternative constructions are relatively more complex in construction and operation.
Accordingly, it would be a substantial advance in the art to provide a plunger construction which is engageable with the driving mechanism of an angiography power injector apparatus, and overcomes the aforementioned deficiencies of the plunger constructions described above.
Accordingly, it is an object of the present invention to provide a plunger which is readily engageable with the driving mechanism of a power injector, and overcomes the aforementioned deficiencies of the prior art plunger and syringe structures.
It is another object of the present invention to provide an angiography syringe comprising such a plunger.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.